May 11, 2013

Experimental Cocaine Vaccine Effective On Mice, Primates

Although trends are pointing to a decrease in recent years, cocaine use is still a major problem in the US, with 1.5 million users in 2010 — according to the Substance Abuse and Mental Health Services Administration (SAMHSA).

To combat this highly addictive illegal drug, researchers at Weill Cornell Medical College are developing an “anti-cocaine vaccine” designed to keep the drug from creating the dopamine-induced high in the brain.

"We believe this strategy is a win-win for those individuals, among the estimated 1.4 million cocaine users in the United States, who are committed to breaking their addiction to the drug," he said. "Even if a person who receives the anti-cocaine vaccine falls off the wagon, cocaine will have no effect."

The vaccine, developed by Crystal and his colleagues, combines elements of the common cold virus with a particle designed to replicate the structure of cocaine. When the vaccine is injected, the body detects the cold virus and releases an immune response against both the virus and the cocaine-like structure.

"The immune system learns to see cocaine as an intruder," Crystal said. "Once immune cells are educated to regard cocaine as the enemy, it produces antibodies, from that moment on, against cocaine the moment the drug enters the body."

For the first part of the study, the researchers injected the vaccine into laboratory mice and observed a strong immune reaction. Vaccinated mice were also observed behaving less erratic than non-vaccinated mice when both were administered cocaine. Antibodies extracted from the mice were also found to neutralize cocaine in test tubes.

For the second part of the study, the researchers sought to find out how effective the anti-cocaine vaccine is in non-human primates. To so do, they needed to measure how much cocaine attached to the dopamine transporter. If cocaine is in the brain, it binds to the transporter, keeping it active in the neural synapses, producing a drug high.

In the study, the researchers attached a short-lived radioactive tracer to track the activity of dopamine transporter in the brain of their laboratory primates. Previous human studies have shown at least 47 percent of the dopamine transporter had to be occupied by cocaine to produce a drug high. The radioactive technique showed that in vaccinated primates cocaine occupancy of the dopamine receptor dropped to levels of less than 20 percent.

"This is a direct demonstration in a large animal, using nuclear medicine technology, that we can reduce the amount of cocaine that reaches the brain sufficiently so that it is below the threshold by which you get the high," Crystal said.